We do not consider single nerve cell as possessing intelligence. And again, mold doesn't solve maze. It isn't even aware of maze. It is following a rigid and very simple program. If you draw the line of intelligence here, literally all living beings are intelligent. And all computers too

Don't those usually refer to single entity traversing maze? Not something that can just grow in all directions

It's not an optimized search algorithm. It's literally "spread yourself in all directions, once food signal from one of your sides gets sufficiently strong, shift your body in this direction". It's bruteforce. And no one will put arbitrary line that close to complete unintelligence

For problem-solving animal, it is not seen as sign of intelligence. Imagine if people were saying that "dogs are intelligent, just look at them finding food via smell!"

Do you realize that "slime mold solving maze" is literally just following the steepest gradient of smell/taste of whatever it is in the middle? There is no intelligence involved. And i don't think memory is considered to be a sign of any high intellogence